1. Technical Field
This invention relates to a means of lowering the operational temperature for elastomeric seals and, more particularly, to a specifically shaped seal configuration which limits relative axial movement.
2. Discussion
The elastomeric seal is used in a number of applications where fluids are being transmitted. It is desired to use particular elastomeric compounds in the seals, because of that compound's resistance to a chemical, or range of chemicals.
Traditionally due to the structure and composition of seals, leakage tends to occur over time when chemical fluids are transmitted through the sealed area. This is especially true of fluroelastomers when the chemical fluids are at temperatures lower than minus 25.degree. Fahrenheit. The problem arises because the elastomer fails to recover from a deformation within the time required to maintain the sealed relationship between the components being sealed. The problem is not one of the diameters which confine the seal, or the gland link that confines the seal, because they are constant at the temperature and because of thermal inertia do not change more rapidly than the seal can accommodate. The problem is with changes in the coaxiality of the two diameters. In normal situations, the non-rotating relative movements of the two components which are caused by forces developed as a result of movements which are a part of the dynamic operation of the machine or device for which the seal connection is a portion of, cause a changing coaxiality of the two diameters which is limited in off coaxiality movement by the physical structure of the sealed joint.
Normal manufacturing tolerances yield limits to this relative axis movement which are in excess of the seal material's ability to follow these changes by changing shape and thus maintain the seal. When this condition exists, the seal is not operative, and will leak.
There is however, a method of establishing a situation where these relative axial movements are limited to a much greater extent, that permits the seal to be operational to a much lower temperature, while still allowing relative rotation of the two components.
By using a bearing system for the two components that allows rotation, but limits axial differences to less than those which can be followed by the seal, the maintenance of a sealed relationship is possible. By reaming holes of repeatable size and sizing of outside diameters in the areas of the interior part of the rotating combination, it is possible to achieve the required limitations for seals of even and O-ring configuration that allow a sealed relationship of rotating parts at temperatures lower than those that can be achieved by normal methods of fabrication, which do not achieve the very close fits required.
It is not a situation that requires a new fabrication ability, or a special manufacturing process for seals, it is the recognition that by doing things this way that it is possible to lower acceptable operating temperatures. Also, it is possible to have one of the components which confine the seal form the other, and achieve a line to line rotating fit.